Thermodynamics Flashcards
thermal equilibrium
when no heat flows between objects
What changes as a function of temperature
length, volume, solubility and conductivity
Length expansion equation
ΔL=αLΔT
α = coefficient of linear expansion
Volumetric expansion equation
ΔV=βVΔT
β = 3α
isolated systems
not capable of exchanging energy or matter with their surroundings
total change in internal energy must be zero
closed systems
capable of exchanging energy but not matter with surroundings
Open systems
can exchange both matter and energy with the environment
matter can carry energy and can be transferred in the form of heat or work
state functions
path independent to get to particular equilibrium state
pressure, density, temperature, volume, enthalpy, internal energy, gibbs free energy, and entropy
process functions
depend on the path taken to get from one state to another
work and heat
first law of thermodynamics
change in the total internal energy of the system is equal to the amount of energy transferred in the form of heat to the system minus the amount of work transferred in the form of work
ΔU = Q-W
energy cannot be created or destroyed, only exchanged
positive Q
heat flows into the system
negative Q
heat flows out of the system
positive W
work is done by the system (expansion)
negative W
work is done on the system (compression)
negative ΔU
decreasing temperature
positive ΔU
increasing temperature
second law of thermodynamics
objects in thermal contact and not in thermal equilibrium will exchange heat energy such that hotter object gives heat to colder object
increase entropy
Heat
process by which a quantity of energy is transferred between two objects as a result of a difference in temperature
heat cannot be spontaneously transfer energy from a cooler to a warmer object without work being done on the system
Calorie to Joules
1 Cal = 10^3 cal = 4184 J
Conduction
transfer of energy between objects through molecular collisions
must have direct physical contact between objects
hotter object transfers some kinetic energy to particles of cooler matter through collisions between the particles of the two materials
ex: touching a hot stove
What are the best heat conductors?
metals because metallic bonds contain density of atoms embedded in sea of electrons which facilitates rapid energy transfer
What are the poorest heat conductors?
gases because there is so much space between individual molecules which makes energy-transferring collisions occurring infrequently
convection
transfer of heat through physical motion of the fluid over the material
only liquids and gases can use this
ex: convection ovens circle hot air inside the oven which causes rapid cooking
ex: using an ice bath to rapidly cool something
Radiation
transfer of energy by electromagnetic waves (through a vacuum)
ex: way sun is able to warm the earth
specific heat
amount of heat energy required to raise one gram of a substance by one degree C/K
changes depending on phase
q=mcΔT
specific heat of water
1 cal/g*K
What happens when you add heat to ice?
the heat energy causes water molecules to move away from one another because breaking hydrogen bonds
now the water molecules are held less rigidly in place and have greater degrees of freedom of movement, average PE increases
equation for phase change
q = mL
q = amount of heat gained or lost m= mass of substance L= heat of transformation
heat of fusion
heat of transformation between solid and liquid (either direction)
heat of vaporization
heat of transformation between liquid and gas
melting
solid to liquid
freezing
liquid to solid
condensation
gas to liquid
evaporation/vaporization
liquid to gas
sublimation
solid to gas
deposition
gas to solid
isobaric
pressure held constant
isothermic
constant temperature
ΔU=0
W=Q
isochoric
isovolumetric
constant volume
W=0
ΔU=Q
adiabatic
no heat exchange
Q=0
ΔU= -W
entropy
measure of spontaneous dispersal of energy at a specific temperature
ΔS = Q/T
entropy increases when energy is distributed into a system at a given temperature
the entropy of a system can decrease when?
the entropy of surroundings increases by at least as much
because the entropy of the universe must remain constant or increase during all processes
1 mole = how many liters at STP
22.4L
gas constants
- 0821 atm L/mol K
8. 314 J/mol K
Gay Lussac’s Law
Pressure is directly proportional to Temperature
P1/T1 = P2/T2
Charles’ Law
Temperature is directly proportional to volume
V1/T1 = V2/T2
Avogadro’s Law
volume is proportional to number of moles
V1/n1 = V2/n2
Boyles’ Law
Pressure is inversely proportional to volume
P1V1 = P2V2
Van der Waals equation
(P + a(n/v)^2)(V-nb) = nRT
Boltzman’s Constant
PV = NkbT
kb=n/NR
kb=1/Na(R)
N= nNa (number of moles x avogadro’s number)
kb=1.38x10^-23 J/K
allows us to find ideal gas law focusing on number of molecules
internal energy
Uint = 3/2PV = 3/2NKbT = 3/2nRT
equal to internal energy
changing internal energy
ΔU = Q + W
if you are doing work on gas = +W
if the gas is doing work = -W
W = PΔV
What is the work done when pressure is constant
W = PΔV
heat capacity
if a certain amount of heat is added, how much will the gas expand
C= Q/ΔT
molar heat capacity
C = Q/nΔT
when at constant volume
C = 3/2R
when at constant pressure
C=5/2R
heat capacity (volume)
keeping the volume the same will increase pressure as we add more heat
C = Q/ΔT
no work can be done because no expansion; will heat up
Cv = ΔU/ΔT = 3/2PV/ΔT = 3/2Nkb = 3/2nR
Cv=3/2nR
heat capacity (pressure)
work can be done on the gas
Cp = Q/ΔT = ΔU-W/ΔT = ΔU-PΔV/ΔT = 3/2nRΔT + PΔV/ΔT = 3/2nRΔT + nRΔT/ΔT = 3/2nR + nR = 5/2 nR
Cp = 5/2nR
force equation
F = ΔP/ΔT = mΔv/ΔT
